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Introduction

Pulmonary embolism (PE) is a potentially life-threatening condition associated with a partial or complete obstruction of the pulmonary artery caused by a thrombus that breaks off from a peripheral vein, migrates via the right side of the heart, and lodges in the pulmonary artery circulation. About 90% of emboli originate from venous thrombi in the lower extremities and pelvis. The presence of emboli in the pulmonary vasculature blocks normal blood flow to the lung and increases pulmonary resistance. This, in turn, increases pulmonary artery pressure and right ventricular pressure. When greater than 50% of the vasculature is occluded, the patient experiences significant pulmonary hypertension and acute cor pulmonale. Undetected, this leads to long-term morbidity and death.

PE is the third most common cause of death from cardiovascular disease, with approximately 650,000 cases of PE occurring per year in the United States. The diagnosis is frequently missed, with 30% of cases diagnosed antemortem. Massive PE occurs in only 5% of cases, but has an associated mortality rate of 40%. Overall, mortality is 3–10% if treated and 15–30% if untreated.

Clinical Presentation

History

The classic triad of chest pain, dyspnea, and hemoptysis is present in fewer than 20% of patients. Dyspnea is the most common symptom associated with PE, occurring in up to 80% of confirmed cases, with 67% experiencing rapid onset of shortness of breath. Pleuritic chest pain is present in 52% of patients, but substernal chest pain is present in <20%. Other symptoms include fainting, cough, palpitations, hemoptysis, and calf/thigh pain or swelling.

Physical Examination

Tachypnea (≥ 20/min) is one of the most sensitive clinical findings, with a prevalence of 70% in PE confirmed cases. Tachycardia (≥100/min) has a prevalence of 26%. Pulse oximetry is frequently normal in patients with a PE and cannot be used to exclude the diagnosis. Lung examination may be clear or may reveal rales, whereas extremity examination is useful only if signs of a DVT are present. Rectal examination for blood is useful to assess bleeding risk if anticoagulation becomes necessary.